Field of the Invention
The present invention relates to a pattern selecting device of a sewing machine, and more particularly to a device for enabling a sewing machine operator to select a desired one of the pattern cams in any angular position of a main drive shaft of the sewing machine. More precisely according to the invention, a cam follower may be manually disengaged from one of the pattern cams and engaged to a newly selected pattern cam in any one of the plurality of angular positions of the main drive shaft of the sewing machine, that is, even if a machine needle remains in a fabric to be sewn when the sewing machine is standstill. Further the manually disengaged cam follower may be automatically engaged with the newly selected pattern cam when the sewing machine is driven and the main drive shaft comes to a predetermined angular range in which the machine needle is located above the fabric.
A sewing machine having a conventional pattern cam selecting device generally requires a considerable amount of manual force each time in order to disengage a cam follower from one of the pattern cams in the pattern cam selecting range because the cam follower is normally spring-biased toward the pattern cams. To eliminate such a problem, some sewing machines have been provided with a mechanism for holding the cam follower in a condition in which it is disengaged from the pattern cam when the cam follower is once disengaged until the follower is brought to the engagement with the newly selected pattern cam. The sewing machine may be further provided with a mechanism which is manually and/or automatically (in the initiation of the drive of the sewing machine) operated to release the cam follower so as to engage the newly selected pattern when the follower was brought to the newly selected pattern cam.
However, in such conventional sewing machines, the disadvantage of the cam follower releasing mechanism resides in preventing the pattern cam selecting operation from being performed within a certain angular range of the main drive shaft of the sewing machine. The cam follower releasing mechansim may include an actuating cam rotated in association with the main drive shaft or a lower drive shaft, a follower lever cooperating with the actuating cam to release the cam follower and a toggle spring for pressing the follower lever against the actuating cam until the cam follower is released from the disengaged position, and then for holding the follower lever at a position spaced from the rotation path of the actuating cam when the cam follower has been released. In this case, the follower lever is moved to a stopper with the force of the toggle spring which is amplified with the inertia of the actuating cam which pushes the follower lever. The follower lever will therefore hit the stopper producing a high impact sound and accordingly giving an adverse influence to the endurance of the associated elements.